Control of Trogoderma granarium (Coleoptera: Dermestidae) Using High Temperatures.

Khapra beetle, Trogoderma granarium Everts, is one of the world's most important pests of stored grain. Common in Africa and Asia, it is a quarantine insect for much of the rest of the world where methyl bromide has traditionally been used for its control. However, this ozone-depleting fumigant is now heavily restricted, and alternate methods of control are required. In a two-step process, we examined the use of high-temperature exposure as one such method of control. First, different life stages were held at 45°C for different periods to calculate LT50 (lethal time to 50% mortality) values. In descending order, the most heat-tolerant life stages at 45°C were diapausing larvae (LT50 = 41 - 122 h) > nondiapausing larvae (LT50 = 47 h) > adults (LT50 = 33 h) > pupae (LT50 = 25 h) > eggs (LT50 = 10 h). Second, diapausing larvae (the most heat-tolerant stage) were held at 45, 50, 55, and 60°C for different periods to calculate LT50, LT95, LT99, and probit 9 (99.9968% mortality) values. Estimated LT99 values for diapausing larvae were 288 h at 45°C, 6 h at 50°C, 1.1 h at 55°C, and 1 h at 60°C. Based on these results, an exposure of 2 h at 60°C is recommended to control T. granarium with high temperatures. To meet requirements for control of quarantine pests, exposure of between 2 and 12 h at 50-60°C is recommended to cause probit 9 mortality, but additional experiments are needed to get a better estimate of probit 9.

Effects of Tetracycline and Rifampicin Treatments on the Fecundity of the Wolbachia -Infected Host, Tribolium confusum (Coleoptera: Tenebrionidae).

We examined the effects of Wolbachia bacteria on the reproduction of the flour beetle Tribolium confusum (Coleoptera: Tenebrionidae) using different antibiotics and across generations. We first removed infections by rearing insects on a diet with tetracycline (T; 1.0, 2.0, 3.0, 5.0, 10.0 mg/g) or rifampicin (R; 0.1, 0.2, 0.3, 0.5, 1.0 mg/g). We then performed experimental crosses using adults two generations (G2) and four generations (G4) removed from antibiotic treatments. Results showed that use of rifampicin more readily cured infections. Egg hatch from crosses of uninfected females and infected males was 0, but averaged 84 to 91% for eggs from all other crosses. Elevated fecundity was observed for T-G2 females, but not for T-G4, R-G2, or R-G4 females. Cross type had little or no effect on the sex of F 1 offspring, which averaged 52% female. These collective results support previous findings that show that Wolbachia in T. confusum causes 100% cytoplasmic incompatibility and emphasize that the antibiotic treatment used to remove infections may have additional consequences (e.g., elevated fecundity) that may not be apparent in subsequent generations.

Effect of temperature and relative humidity on the cellular defense response of Ephestia kuehniella larvae fed Bacillus thuringiensis.

While maintained under all combinations of three temperatures and two RH, fifth instar larvae of the Mediterranean flour moth, Ephestia kuehniella were fed wheat treated with spores and crystals of Bacillus thuringiensis var. kurstaki. Larvae that had fed on wheat with the bacterial preparation contained higher concentrations of nodules in their haemocoel than did larvae fed on wheat without bacteria. Nodule concentrations in larvae fed untreated wheat were unaffected by temperature or relative humidity. Larvae fed treated wheat had higher nodule concentrations at 32 degrees C than at 15 and 23 degrees C, and higher nodule concentrations at a relative humidity of 85% than at 43%. The percentage of larvae that pupated was lower when larvae were fed the bacterial preparation, and was significantly higher at 23 degrees C than at 15 and 32 degrees C, regardless of whether larvae were fed bacteria or not. Less time was required for larvae to develop to pupation at higher temperatures and at higher humidity. Mean time to pupation was lower for bacteria-fed larvae than for those fed untreated wheat, and this appeared to be a result of truncation of the distribution of times to pupation because only rapidly developing larvae survived to pupation.

Repellent effect of pea (Pisum sativum) fractions against stored-product insects.

Peas (Pisum sativum) are toxic to some stored-product insects. The repellent effect of fractions of pea seed to stored-product insects was evaluated in multiple-choice tests in which wheat kernels were dusted with fractions rich in either protein, fibre or starch at 0.001 to 10% (wt:wt). There was a negative correlation between pea protein concentration and the number of adults found in grain for Cryptolestes ferrugineus and Sitophilus oryzae, but not for Tribolium castaneum. Pea fibre repelled C. ferrugineus adults but not S. oryzae and T. castaneum. Pea starch did not repel any of the insects. One-week old and 6-week old C. ferrugineus were equally repelled by pea protein. Repellency was detectable 1h after exposure. Cryptolestes ferrugineus and S. oryzae did not become habituated to the repellent action of pea protein even after 4 weeks of exposure. Habituation was observed, however, when C. ferrugineus was exposed to pea fibre for 4 weeks. In a two-choice bioassay (0 vs. 0.1% and 0 vs. 1% pea protein), the pea-protein-treated grain had significantly fewer insects (C. ferrugineus, S. oryzae, Sitophilus zeamais, T. castaneum, and Tribolium confusum) than untreated grain. The properties of the pea protein fractions seem well suited for developing a natural stored grain protectant.

The effect of cold acclimation and deacclimation on cold tolerance, trehalose and free amino acid levels in Sitophilus granarius and Cryptolestes ferrugineus (Coleoptera).

Canadian and French laboratory strains of Sitophilus granarius (L.) and Cryptolestes ferrugineus (Stephens) were cold acclimated by placing adults at 15, 10 and 5 degrees C successively for 2wk at each temperature before deacclimating them for 1wk at 30 degrees C. Unacclimated S. granarius had an LT(50) (lethal time for 50% of the population) of 12days at 0 degrees C compared with 40days after the full cold acclimation. At -10 degrees C, unacclimated C. ferrugineus had an LT(50) of 1.4days compared with 24days after the full acclimation. Cold acclimation was lost within a week after returning insects to 30 degrees C. Trehalose, as well as the amino acids proline, asparagine, glutamic acid and lysine were higher in cold acclimated insects for both species. For S. granarius, glutamine was higher in cold acclimated insects and isoleucine, ethanolamine and phosphoethanolamine, a precursor of phospholipids, were lower in cold acclimated insects. For C. ferrugineus, alanine, aspartic acid, threonine, valine, isoleucine, leucine, phenylalanine and phosphoethanolamine were higher in cold acclimated insects. For both species tyrosine was lower in cold acclimated insects. There were small but significant differences between Canadian and French strains of S. granarius, with the Canadian strain being more cold hardy and having higher levels of trehalose. There were small but significant differences between male and female S. granarius, with males being more cold hardy and having higher levels of proline, asparagine and glutamic acid. In conclusion, high levels of trehalose and proline were correlated with cold tolerance, as seen in several other insects. However, correlation does not prove that these compounds are responsible for cold tolerance, and we outline further tests that could demonstrate a causal relationship between trehalose and proline and cold tolerance.

The effects of carbohydrate-enriched meals on glucose turnover and metabolic clearance rates of glucose in type 2 diabetic patients.

The addition of fructose to natural meals elicits lower serum glucose and immunoreactive insulin responses when compared with that of sucrose and starch meals. Differences in rates of splanchnic glucose appearance and peripheral glucose disposal may be partly responsible. To evaluate the role of both parameters after different carbohydrate-enriched meals, we measured the arterialized venous blood glucose, immunoreactive insulin and gastric inhibitory polypeptide concentrations in seven Type 2 diabetic patients after ingestion of isocaloric test meals. Measurements were made in a random manner on three separate occasions. Fructose, sucrose, and bread supplementation constituted 68% of the total carbohydrate content of each meal. Rates of total glucose appearance, glucose utilization and metabolic clearance rates of glucose were determined by the D3-H-3 glucose prime-continuous infusion technique. The mean fasting glucose levels were similar in the three groups. Mean peak glucose concentrations and integrated incremental areas were significantly lower (p less than 0.02) after the fructose-enriched meals compared with that of either sucrose or bread. The basal arterialized venous blood glucose levels were similar in all three groups. The mean incremental integrated arterialized venous blood glucose area was significantly lower in the fructose group when compared with the sucrose (p less than 0.05) and bread (p less than 0.02) groups. The mean fasting gastric inhibitory polypeptide levels were similar in the three groups. However, the mean incremental integrated gastric inhibitory polypeptide areas were significantly lower in the fructose group compared with the sucrose and bread groups (p less than 0.01 and p less than 0.05 respectively). Basal hepatic glucose outputs were not significantly different in the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastric inhibitory polypeptide responses and glucose turnover rates after natural meals in type II diabetic patients.

Gastric inhibitory polypeptide (GIP) has insulinotropic actions in the presence of hyperglycemia. However, its extrapancreatic effects on glucose homeostasis are controversial. We have studied the relationships between GIP and immunoreactive insulin (IRI) and glucose turnover rates (D3H-3 glucose technique) in five poorly controlled type II diabetic patients and five normal subjects before and after a breakfast containing 500 kcal including 42 g sucrose. Mean fasting serum glucose levels and glucose responses were significantly (P less than 0.001) higher in the diabetic patients than in normal subjects. Mean basal serum IRI levels were similar in both groups [12.8 +/- 2.9 (SEM) vs. 11.8 +/- 2 microU/ml, P = NS]. After meal ingestion, mean IRI levels rose significantly to a peak at 20 min in the normal subjects but the responses were blunted in the diabetic patients (74 +/- 10 vs. 24 +/- 6 microU/ml, P less than 0.001). At all other times studied (60-180 min), mean serum IRI levels were similar in the diabetic patients and the normal subjects except at 180 min. Mean basal serum GIP levels were similar in the diabetic patients and the normal subjects (538 +/- 100 vs. 400 +/- 50 pg/ml, P = NS). After meal ingestion, mean GIP levels rose between 0-60 min but were significantly higher in the diabetic patients only at 20 min (1200 +/- 190 vs. 566 +/- 76 pg/ml, P less than 0.01). Mean basal hepatic glucose output was higher (P less than 0.01) in the diabetic patients. However, the mean basal MCR values were similar. After meal ingestion, total splanchnic glucose output and rates of glucose utilization (RU) were significantly higher in the diabetic patients compared with the normal subjects (P less than 0.001, and P less than 0.001, respectively). Postmeal MCR values were not statistically different in both groups. There were significant positive correlations between postmeal splanchnic glucose output and both IRI (r = 0.805, P less than 0.005) and GIP (r = 0.749, P less than 0.02) in the diabetic patients but not in the normal subjects (r = 0.10, P = NS for both). Whereas no relationships existed between RU and IRI in either group, RU correlated strongly with GIP (r = 0.810, P less than 0.005) only in the diabetic patients. We hypothesize that GIP may play a compensatory role to improve both impaired beta-cell insulin release and peripheral glucose utilization which are the recognized pathogenetic mechanisms underlying type II diabetes mellitus.

Abnormal retinal artery responses to stress in patients with type I diabetes.

The brachial artery pressure and retinal artery pressure responses to a one-minute cold pressor test were evaluated simultaneously in 14 patients with type I diabetes mellitus (six with and eight without diabetic retinopathy) and 10 age-matched control subjects. Five patients with type I diabetes had autonomic neuropathy. Mean baseline brachial artery pressure and retinal artery pressure were similar in patients with type I diabetes and control subjects. After cold pressor testing, the brachial artery pressure increased significantly (p less than 0.01) compared with baseline values in both groups. Retinal mean arterial pressures increased significantly (p less than 0.001) after cold pressor testing compared with the baseline values only in patients with type I diabetes. Positive correlation was found between the brachial and retinal mean arterial pressures after cold pressor testing (r = 0.48; p less than 0.05) in the diabetic patients but not in the control subjects (r = 0.10; p = NS). No correlation was found between the retinal artery pressure and age of onset of diabetes, duration of diabetes, the presence or absence of diabetic retinopathy, and glycemic control. Four patients with autonomic neuropathy and low retinal artery pressures, which remained unchanged after cold pressor testing, had no diabetic retinopathy. The fifth patient with autonomic neuropathy and exaggerated systolic brachial artery pressure (175 mm Hg) and retinal artery pressure (more than 80 mm Hg) responses had severe background diabetic retinopathy. In conclusion, abnormal retinal artery responses to stress are present in patients with type I diabetes. This may be modified by the presence or absence of both autonomic neuropathy and hypertension. The biologic significance of these findings is yet to be determined.